Phylogenetic tree of clinical isolates (part A, inset) alongside columns representing (from left to right): antibacterial activity of wild-type (WT) and T6SS-inactive (ΔtssE) mutants of each clinical S. marcescens isolate against E. coli and S. marcescens SM39 target organisms, antibacterial activity of wild-type isolates against a Pseudomonas fluorescens (Pf) target, and Hcp secretion by wild-type and ΔtssE strains at 30°C and 37°C. For antibacterial activity, the number of recovered target cells following co-culture with the indicated strain of S. marcescens plotted (mean of four replicates). For Hcp secretion, the amount of secreted Hcp determined by immunoblotting is plotted (mean of two replicates). The darker the color, the higher the level of antibacterial activity (i.e., the lower the number of recovered target cells) or the higher the level of Hcp secretion. Examples of anti-Hcp immunoblots of cellular and secreted fractions and individual co-culture assays are shown on the right, and the full data are in Figure S2.
